PNU-142731 is a pyrrolopyrimidine, non-corticosteroid anti-inflammatory agent developed by the Pharmacia & Upjohn Pharmaceutical Company to be used in asthma patients. It is an oral, once daily agent proposed for use in the chronic treatment of asthma. Animal studies have shown that PNU-142731 can ameliorate both the early-phase and late-phase asthmatic response. Three human trials have shown that PNU-142731 is tolerated well by humans. The proposed study is a double-blind, randomized, placebo-conrolled trial of two doses of PNU-142731 to evaluate the efficacy and safety of PNU-142731 in subjects with moderate persistent asthma. The end-points of the study include direct measures of asthma including lung function, daily symptom logs, and beta-agonist use as well as indirect measures of asthma such as assessment of inflammatory markers in induced sputum and serum. A secondary purpose of this study is to validate the use of asthma quality-of-life (QOL) questionnaires in clinical trials.